Answer:
a. 

b. 

Step-by-step explanation:
Hello, 
a. 
One could consider the following equation for this exercise's first part:

Whereas 
 is the density, 
 the acceleration of gravity, 
 the height and 
 the atmospheric pressure, thus:

b. 
Now, to know the pressure on the diver's body, one uses the following equation considering that the pressure is exerted downwards:

Best regards.